1. Field of the Invention
This invention relates to a multilayer substrate having a capacitor section.
2. Description of the Background
For increasing the wiring density of circuit substrates, it was proposed in Electroceramics, vol. 18, No. 5 (1987) to build capacitors in multilayer substrates. When such multilayer substrates are prepared, the conductor material, dielectric material and substrate material must be concurrently fired. Since the firing temperature used is generally below the melting point of the conductor material, glass-ceramic composite substrate materials having a low firing temperature must be used when silver and silver-palladium having a low melting point despite satisfactory properties and low cost are used as the conductor material. The glass-ceramic composite substrates contain glass powder as well as a filler such as Al.sub.2 O.sub.3. Glass powder in which the total content of SiO.sub.2 and B.sub.2 O.sub.3 is more than about 30% by weight as described, for example, in JP-A 230606/1990 is often used as the glass powder in order to reduce the softening point and improve the wettability to the filler.
On the other hand, dielectric materials having a high dielectric constant must be used in order to produce compact high-capacity capacitors. For example, lead-base perovskite compounds are deemed promising since they have a dielectric constant of higher than 10,000 and can be co-fired with silver. (See Circuit Technology, 6, 1, 28 (1991); the 1st Microelectronics Symposium (July 1985, Tokyo), p73; and IEMT Symposium (1993, Kanazawa), p70.)
Further when lead-base perovskite compounds are utilized as thick film devices (functional films of about 10 .mu.m to about 30 .mu.m thick) such as capacitors, a binder such as glass and sintering aids must be added thereto.